Discrete sounds better than integrated? a possible reason

[Winston OBoogie]

I have often wondered if a big part of the general opinion that discrete = sound better is that dont discrete circuits tend to clip asymmetrically with respect to the Positive and negative rails?

Some do.  Some don't.  All kinds of misbehaviors -  slew rate limiting, VAS/TIS clipping before output stage, simple compensation schemes that limit fb at H.F.,  ... anything really.

You could design a discrete with staggered rails, off the charts headroom on all stages, whatever you desire.
I'm just trying to make the point that discrete needn't sound like anything.  There is no one discrete sound in my opinion.

Keep in mind that a lot of the circuits folks clone/copy on here were designed when transistors were expensive and still fairly new.  So you see a lot of 3 transistor gain stages.  This was really down to economy, of money and possibly knowledge?  Also borne out of working with tubes so you see similar topologies being adopted with early Germanium & BJT

For the record, I'm not at all knocking these early efforts. 
It's all good  8)

 

[ruffrecords]

Hello

The nevegate  ;D
Faked THD emission measurement for aproval  8)
I guess the one programming the software that recognise the test bench situation and minimise compromising data will have trouble wih regulation

Best
Zam

LOL. Storm in a tea cup. The object was to verify correct operation of the Neve parts of the mixer not the distortion of the VU meter.

Cheers

Ian

 

[abbey road d enfer]

The object was to verify correct operation of the Neve parts of the mixer not the distortion of the VU meter.

But were customers informed of this degradation? I don't remember having seen such caveat when I was in charge of the infamous Barclay desk.
Why didn't Neve provide meter buffers?

 

[ruffrecords]

But were customers informed of this degradation? I don't remember having seen such caveat when I was in charge of the infamous Barclay desk.
Why didn't Neve provide meter buffers?

They did provide the option of regular VU meters, buffered ones or PPMs (Pete Townshend had PPMs on his Neve desk). I do not know why but most people chose unbuffered VUs. Unbuffered VUs were common everywhere back in the 70s when I was there.

Cheers

Ian

 

[abbey road d enfer]

They did provide the option of regular VU meters, buffered ones or PPMs (Pete Townshend had PPMs on his Neve desk). I do not know why but most people chose unbuffered VUs. Unbuffered VUs were common everywhere back in the 70s when I was there.

Cheers

Ian

It would be interesting to know if this choice was purely economic, or distortion was considered negligible (or even desirable), or if it was pure ignorance.

 

[L´Andratté]

Thanks Ruffrecords and all for discussing this!

This is a mic pre I built with some old Sowter 1:5 transformers (it is a design by Ricardo from a somewhat unnerving GDIY thread, but it is almost exactly to be found in AoE 2nd edition. IIRC GDIY member joechris made me aware of it).
It´s not a NEVE, but very exemplary in "sounding discreeete" :, soft onset of distortion, little harshness, etc. No output buffer for extra loading, it´s a classy low noise distortion pedal...
Of course the transformers are in there too so as ever, grain of salt, etc.

Maybe someone likes to make a point about it.
Maybe not. It´s all I could possibly contribute--

https://groupdiy.com/index.php?topic=64069.msg811214#msg811214

 

[Winston OBoogie]

That circuit of Ricardo's looks good for only using 2  transistors. 
He didn't even bother with the usual emitter follower before Q2 
I like it , I bet it sounds nice on a lot of things. 

Edit:  On reflection, this is typical for early '70's stuff like the Helios pre etc., except, I bet it's a lot quieter.

Very small current (94uA) on the input Q1 which would be about perfect for a 1:5 mic input transformer.
I'm assuming the 3K8 resistor shown as R12 is not really there on the actual circuit but is shown to reflect what the 1:5 transformer will present. 

 

[L´Andratté]

Yes, it´s looking into the secondary

 

[Winston OBoogie]

Yes, it´s looking into the secondary

Yep thanks.

It might have helped had I read the thread you linked to  ???
I have now 

Again, nice.  Thanks for posting.

 

 

[abbey road d enfer]

On reflection, this is typical for early '70's stuff like the Helios pre etc., except, I bet it's a lot quieter.

Why would that be? I reckon a BC109C at the input would not be very different in terms of noise.

 

[Winston OBoogie]

Why would that be? I reckon a BC109C at the input would not be very different in terms of noise.

It isn't the device, it's the fact it's optimized for lowest noise with the source impedance.

You mention the BC109 which is what Neve used early on.
They (Neve) couldn't optimize for lowest noise because the impedance seen by the first BC109 varies depending on attenuator setting. 
This because they chose to not vary the amp gain too much and opted to go for a divider network on the IP transformer secondary.  So the current in the input transistor is at a compromise setting.

On Helios, they used a honking 1:10 input transformer and, with that reflected secondary impedance, we're really into Toshiba extinct J-Fet territory for lowest noise.


Edit:  Impedance seen by input transistor in Neve 10** series modules varies from, circa sub 60 ohms in line input mode, to about 1K4 with attenuator halfway down in mic mode.  This from memory so, subject to checking of maths

 

[ruffrecords]

It would be interesting to know if this choice was purely economic, or distortion was considered negligible (or even desirable), or if it was pure ignorance.

That is a good question but probably hard to answer. I know back in the 70s it was common to connect VU meters directly across outputs. It happened in mixers, in tape machines and external FX boxes. In the course of tracking a mastering in those days, the signal probably experienced several VU meters before it reached the recording medium. One the other hand, in those days most professional gear was designed to be able to drive a 600 ohm load so they had pretty low output impedances - which means they might be less affected by the non linear load of a VU than you might expect.

And on the third hand, I do not think many end users were aware of the distortion that VU meters added.

Cheers

Ian

 

[abbey road d enfer]

It isn't the device, it's the fact it's optimized for lowest noise with the source impedance.

You mention the BC109 which is what Neve used early on.
They (Neve) couldn't optimize for lowest noise because the impedance seen by the first BC109 varies depending on attenuator setting. 
This because they chose to not vary the amp gain too much and opted to go for a divider network on the IP transformer secondary.  So the current in the input transistor is at a compromise setting.

On Helios, they used a honking 1:10 input transformer and, with that reflected secondary impedance, we're really into J-Fet territory for lowest noise.


Edit:  Impedance seen by input transistor in Neve 10** series modules varies from, circa sub 60 ohms in line input mode, to about 1K4 with attenuator halfway down in mic mode.  This from memory so, subject to checking of maths

I understand all that, but your remark, IIUC, was addressed only to the posted schemo.
Regarding the Helios and its 1:10 xfmr, the preamps in my mixers used a similar one (Melodium, if you remember them) with a BC109C operating at 50uA.
I measured -128dBu input noise with a 200r dummy.
About the Neve, the operating point must be chosen for the highest gain, since S/N ratio can only improve, unless someone does crazy things with attenuators.
I have designed a preamp where the input device (BC560) runs at 200uA and normally sees a 2k secondary. I dedicate it to drums and such brutal sources. It is not the quietest in the world but nobody complained so far.
The input pad is based on an alternate primary (20k nominal), so the transistor base sees about 20 ohms+ some DCR, so talk about mismatch! Anyway, the resulting S/N ratio is perfectly manageable and inobtrusive.
And yes, the output stage is class A. 

 

[Winston OBoogie]

That is a good question but probably hard to answer. I know back in the 70s it was common to connect VU meters directly across outputs. It happened in mixers, in tape machines and external FX boxes. In the course of tracking a mastering in those days, the signal probably experienced several VU meters before it reached the recording medium. One the other hand, in those days most professional gear was designed to be able to drive a 600 ohm load so they had pretty low output impedances - which means they might be less affected by the non linear load of a VU than you might expect.

And on the third hand, I do not think many end users were aware of the distortion that VU meters added.

Cheers

Ian

I'm guilty of advising the testers at UA to test distortion on the LA-2A with the meter in gain reduction mode. 
They'd been doing it on the AP after checking line up levels etc.  and the meter was usually left in output monitoring mode.
I took a unit over to my FFT setup and showed them the effect of the meter on the distortion spectra.
It's quite clearly there even with a 600 om load.


Now in my defense, most folks will be using an LA-2A monitoring in gain reduction but, for my sins, flame away!

 

[abbey road d enfer]

And on the third hand, I do not think many end users were aware of the distortion that VU meters added.

Cheers

Ian

And it's a pity. A long time ago, I demonstrated that to a colleague. I showed him the distortion residues on the scope and was horrified.
I understand the motivations for doing without a meter buffer, cost, complexity, more things that can go wrong, lack of confidence in a measurement that is not done on the actual signal, but the deterioration of performance is not negligible, even in times when tape was the dominant distortion factor.

 

[Winston OBoogie]

I understand all that, but your remark, IIUC, was addressed only to the posted schemo.
Regarding the Helios and its 1:10 xfmr, the preamps in my mixers used a similar one (Melodium, if you remember them) with a BC109C operating at 50uA.
I measured -128dBu input noise with a 200r dummy.
About the Neve, the operating point must be chosen for the highest gain, since S/N ratio can only improve, unless someone does crazy things with attenuators.
I have designed a preamp where the input device (BC560) runs at 200uA and normally sees a 2k secondary. I dedicate it to drums and such brutal sources. It is not the quietest in the world but nobody complained so far.
The input pad is based on an alternate primary (20k nominal), so the transistor base sees about 20 ohms+ some DCR, so talk about mismatch! Anyway, the resulting S/N ratio is perfectly manageable and inobtrusive.
And yes, the output stage is class A. 

I knew you knew that,  sorry

Well, I may be mistaken about the Helios then, but I seem to remember an input current higher than your 50uA so, mea culpa. 

On Neve, I remember that noise is optimized not for the highest gain which sees an impedance of 600 - 800 ohms (transformer secondary attenuator full up) but somewhere between that and the 1K4 when it's halfway down.

Maybe I'm just full of crap and remembering wrong! 

I don't remember Melodium no, I'd be interested in any info if you know of any online somewhere. 

 

[abbey road d enfer]

I'm guilty of advising the testers at UA to test distortion on the LA-2A with the meter in gain reduction mode. 
They'd been doing it on the AP after checking line up levels etc.  and the meter was usually left in output monitoring mode.
I took a unit over to my FFT setup and showed them the effect of the meter on the distortion spectra.
It's quite clearly there even with a 600 om load.


Now in my defense, most folks will be using an LA-2A monitoring in gain reduction but, for my sins, flame away!

Fair enough, but I think the user should have been warned. I must be nitpicking...

 

[Winston OBoogie]

Fair enough, but I think the user should have been warned. I must be nitpicking...

On Neve, or the LA-2A?

On Neve, yes because the meters are always there.
On the LA-2A, I did advise they put something in the manual regarding keeping the meter out of monitoring the output signal except to initially check things.

If it made it into the manual I can't say. 


Also, remember this is supposed to be a copy of an old unit so a meter buffer is not an option. 

Anyway, I wonder if any of the plug-in models of vintage devices have an option for "with meter" and "without" because, otherwise it ain't real man! 

 

[abbey road d enfer]

I knew you knew that,  sorry

Well, we must talk of things we take for granted, because others are watching us! They may not know...

I don't remember Melodium no, I'd be interested in any info if you know of any online somewhere.

Well, I was going to write that it is long gone, went bust in the 80's, but I checked and someone has revived the brand. https://www.melodium.fr/fr/
They were known for their microphones, not only the 42B (44BX rip-off), but the 75A, a compression chamber mic (!) that was found in almost every town and village that had some sound equipment. I made a lot of gigs where I sang into the 75A suppled by the local sparky.
But their xfmrs were quite good, with a more than decent mumetal shield.

 

[abbey road d enfer]

On Neve, or the LA-2A?

On the Neve, it should have been discussed at the time of ordering. But I suppose the guy doing the sale would not attract the customer's attention on a sensitive issue. In french, we say "un sujet qui fâche" (a subject that causes anger). 

On the LA-2A, I did advise they put something in the manual regarding keeping the meter out of monitoring the output signal except to initially check things.

That's very considerate.

Also, remember this is supposed to be a copy of an old unit so a meter buffer is not an option.

Do you mean a counterfeit or a recreation?

Anyway, I wonder if any of the plug-in models of vintage devices have an option for "with meter" and "without" because, otherwise it ain't real man!

Maybe the emulation is different according to the meter being in level or in GR...?